U.S. patent number 4,280,161 [Application Number 06/006,922] was granted by the patent office on 1981-07-21 for over-voltage protected, self-contained mobile electrical network system, particularly for automotive applications.
This patent grant is currently assigned to Robert Bosch GmbH. Invention is credited to Walter Kohl, Edgar Kuhn, Gunter Schramm.
United States Patent |
4,280,161 |
Kuhn , et al. |
July 21, 1981 |
Over-voltage protected, self-contained mobile electrical network
system, particularly for automotive applications
Abstract
To protect the battery in an automotive electrical system
against over-charging upon failure of the voltage regulator to
control current flow through the field of an automotive alternator,
the field current is conducted through an interruptable network
element, for example a fuse or a relay controlled switch. A voltage
sensing network, for example a Zener diode, is connected to control
current flow through a controlling element, for example a
thyristor, which provides either an auxiliary current to burn out
the fuse or a control current to the relay coil to interrupt
connection to the field if over-voltage has been sensed.
Simultaneously, an indicator lamp can be energized to indicate
malfunction of the voltage regulator.
Inventors: |
Kuhn; Edgar (Gerlingen,
DE), Kohl; Walter (Bietigheim, DE),
Schramm; Gunter (Vaihingen, DE) |
Assignee: |
Robert Bosch GmbH (Stuttgart,
DE)
|
Family
ID: |
6034617 |
Appl.
No.: |
06/006,922 |
Filed: |
January 26, 1979 |
Foreign Application Priority Data
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Mar 16, 1978 [DE] |
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2811440 |
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Current U.S.
Class: |
361/18; 361/104;
361/55; 361/56; 361/91.6 |
Current CPC
Class: |
H02H
7/065 (20130101) |
Current International
Class: |
H02H
7/06 (20060101); H02H 003/20 () |
Field of
Search: |
;361/18,55,56,91,104
;340/638 ;322/28 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Moose, Jr.; Harry E.
Attorney, Agent or Firm: Frishauf, Holtz, Goodman &
Woodward
Claims
We claim:
1. Overload protected, self-contained mobile electrical network
system having
two d-c terminals;
an electrical generator (G) having its output connected to the d-c
terminals and further having a field winding;
a storage battery (11) connected to the d-c terminals of the
network and to the output of the generator to store electrical
energy therein;
a voltage regulator (6) connected to sense the output voltage of
the generator and intermittently controlling current flow through
the field winding (5) thereof;
and an over-voltage control circuit to prevent damage to the
battery connected to the generator and to continuously and
positively interrupt current flow to the field winding of the
generator upon short circuit within the voltage regulator
including
a fuse (12) connected in series with the field winding (5) of the
generator and to one(-) terminal of the network;
and means providing a control current to said fuse independently of
said voltage regulator under over-voltage conditions of said
network,
comprising
a thyristor (15) having one terminal of its main current carrying
path connected to the other d-c terminal (+) of the network;
a branch circuit (16) from the other terminal of the main current
carrying path of the thyristor to the fuse (12) at a point remote
from said one d-c terminal (-);
a Zener diode providing a reference voltage, connected to and
controlling application of a trigger voltage to the gate terminal
of the thyristor to cause the thyristor to become conductive when
the output voltage from the generator has a prohibited excess
relationship with respect to said reference voltage, whereby
conduction of said thyristor will apply short circuit current
directly from said other d-c terminal (+) of the network through
the branch circuit (16) to the fuse and to the one d-c terminal (-)
of the network to cause the fuse to burn out under loading by said
short circuit current and thereby interrupt current flow to the
field winding (5) regardless of the conduction condition of the
voltage regulator.
2. System according to claim 1, further including a voltage divider
(17, 18, 19) connected to an output of the generator (G),
the Zener diode (14) being connected to the tap point of the
voltage divider and providing said reference voltage as a function
of the voltage on the tap point (17) of the voltage divider.
3. System according to claim 1, further including a voltage divider
(17, 18, 19) connected to an output of the generator (G),
the Zener diode (14) being connected to the tap point of the
voltage divider and providing said reference voltage as a function
of the voltage on the tap point (17) of the voltage divider;
and a filter capacitor (21) connected across at least one of the
resistors (19) of the voltage divider to prevent spurious response
of the Zener diode to short-time stray voltage peaks or
interference pulses.
4. System according to claim 1, for use in a vehicular on-board
electrical network supply system, wherein the generator (G) is a
three-phase alternator and includes a rectifier array (2, 3, 4)
rectifying the output from the alternator and providing said
rectified output to the battery (11), the rectifier including a
diode array (8) providing rectified current to the field (5)
thereof;
a charge indicator lamp (9) is provided connected between the
supply terminal from the field rectifier array to the field and the
output of the rectifier supplying current to the battery;
and further comprising, in accordance with the invention, a bleeder
resistor (20) connected between the field terminal and the other
output terminal of the rectifier array, and hence of the battery,
to provide an energization current to the indicator if current flow
through the field (5) is interrupted upon conduction of said
thyristor (15) and consequent interruption of the field current by
said fuse 12.
Description
The present invention relates to a self-contained mobile electrical
network system, and more particularly to a network system for
installation on automotive vehicles, boats, or the like, in which
the output voltage of an alternator is controlled by repetitively
energizing the field winding of the alternator.
BACKGROUND AND PRIOR ART
Self-contained electrical network systems are used frequently on
board of a automotive vehicles, boats, or the like, and typically
are supplied with power from electrical generators which have a
battery connected to the output to supply power when the generator
is not operating and, in some cases, also excitation voltage. In
typical installations, the generators are three-phase alternators,
driven from an internal combustion (IC) engine with a stationary
armature. A rotating field is provided, supplied with current over
slip rings. The field current is supplied in pulses under control
of a voltage regulator. Customary voltage regulators frequently use
a semiconductor element, typically a power transistor, to control
the current flow through the field winding of the alternator in
dependence on output voltage. The output voltage of the alternator
is compared with a reference value, for example by use of a Zener
diode, which causes the transistor to become conductive if the
voltage drops below the reference value and to block the transistor
if the voltage exceeds the reference value.
If the controlling element of the voltage regulator, for example
the power transistor, or a similar switching element which may be a
solid-state switching element, becomes defective and remains
continuously conductive, for example, in case of a power transistor
if the transistor is short-circuited or alloys, field current is
continuously supplied to the field of the alternator causing the
generator voltage to rise to excessive levels. The mobile power
supply systems have batteries which, if they are charged with
voltages in excess of their design or nominal value for an
excessive period of time become hot and, due to the constant
over-charge, will lose battery fluid and eventually will be damaged
or even destroyed by the continued over-charge. The customary
indicating systems which are used in automotive application provide
for an indication, for example by illumination of a control lamp,
that the alternator is not supplying sufficient current to the
battery to keep the battery charged and to supply loads thereto;
these systems do not, however, indicate to the operator that the
voltage regulator became short-circuited and that the battery is
being over-charged. Damage to the voltage regulator in the sense of
a continuously conductive voltage regulator, is usually not noticed
until the electrolyte of the battery is so depleted that the
battery already is damaged or destroyed. So long as some
electrolyte remains, the various loads connected to the electrical
system will operate since the generator continues to supply power.
Charge indicator lamps in automotive electrical systems are usually
so connected that the positive battery terminal is connected to the
positive field terminal and if the field voltage and battery
voltage are essentially the same--a condition which pertains when
the alternator is charging--the lamp will be extinguished. The
operator, therefore, does not have a device which permits
monitoring of proper operation of the voltage regulator both with
respect to under-charging as well as with respect to overcharging
of the battery.
THE INVENTION
It is an object to provide a monitoring system for self-contained
electrical network systems in which over-voltage conditions can be
sensed and, if they occur, current through the field winding of a
generator supplying the system is disconnected to prevent damage to
the battery which forms part of the system.
Briefly, the field winding is connected to a circuit component such
as a fuse, a switch, preferably a relay controlled switch, or the
like, which is caused to burn out or to open upon sensing of
over-voltage conditions. The over-voltage conditions themselves can
be sensed by means of a Zener diode which, upon breakdown, controls
a control element, for example a thyristor, to supply burn-out
current to a fuse or to control the relay coil of a relay to open
the circuit through the field. Simultaneously, a charge indicator
lamp or a separate indicator lamp can be caused to light so that
the operator will be warned that malfunction exists in the
electrical system. Of course, disconnection of the field from the
alternator causes loss of charge to the battery so that the
remaining operating range of the vehicle will be limited if engine
operation depends on electrical supply, for example to supply
ignition energy thereto. Yet, under usual conditions, the battery
will hold sufficient charge to permit continued operation of the
vehicle for some time, for example to reach a repair station or
other assistance.
The system has the advantage that malfunction of the voltage
regulator by continued conduction thereof is sensed and destruction
of or damage to the battery or other connected elements, due to
excessive supply voltage and over-charge of the battery, is
avoided. The excitation of the generator is interrupted so that the
generator voltage drops to zero.
The system readily permits use of the customary charge control lamp
to indicate malfunction in the charging system by providing a
connection resistor which permits a bypass current of sufficient
current carrying capability to cause the charge indicator lamp to
light. A separate "voltage regulator shorted" indicator lamp also
can be provided.
Use of a fuse in series with the voltage regulator, which is burned
out by a separate burn-out current supplied as a function of output
voltage, is a simple and easily connected control element. Upon
sensing of over-voltage, a short circuit current between the
terminals of the battery is deliberately conducted through the fuse
to cause the fuse to burn out; this short circuit current is
greatly in excess of the normal current flow through the field of
the alternator and the fuse dimensioning and operating
characteristics therefore are essentially non-critical.
DRAWINGS
Illustrating two examples:
FIG. 1 is a schematic diagram of an automotive on-board electrical
network with the over-voltage control circuit of the present
invention connected thereto; and
FIG. 2 is a circuit diagram similar to that of FIG. 1 and
illustrating another embodiment.
The invention is applicable to various types of electrical
generator systems in which over-voltage conditions due to excessive
field current is to be detected; it will be explained in connection
with a typical automotive-type electrical supply system.
Application of the system to other fields will then be clear.
A three-phase alternator G has three armature windings collectively
shown at 1 and respectively connected to a three-phase bridge
rectifier formed of a set of positive diodes 3 and a set of
negative diodes 4, to provide output power at respective terminals
B+ and B-. In addition to the power rectifier array 2 formed by the
diode sets 3, 4, an additional set of diodes 8 is provided to
supply field current to the field winding 5 of the alternator G.
The flow of field current through the field winding 5 is controlled
by a voltage regulator 6. The voltage regulator 6 may be of any
known construction; its output or power circuit has a controlled
switch 7 therein, typically a transistor which is controlled to
become conductive or to block in dependence on output voltage
appearing across the terminals B+ and B- or the voltage between the
exciter diode set 8, measured at the terminal D+ and D-, the latter
being the same terminal as the terminal B-. The type of voltage
regulator, and its internal construction, is not here material and
may be any well known mechanical or solid-state voltage regulator.
The field 5 is connected to a terminal DF, in accordance with well
known notation, which is the same as terminal P1 of the voltage
regulator 6. The material portion of the voltage regulator 6, for
the purposes of the present invention, is the output switch 7 which
opens and closes to provide power of selective duty cycles to the
field 5 as determined by comparison of the output voltage with a
reference.
A charge control lamp 9 is connected through a switch 10 which, in
an automotive vehicle, is the ignition switch, between the
connection of the exciter diodes 8, that is, terminal D+ and the
output power line from the diodes 3, that is, terminal B+. Lamp 9
will light if the voltage between the terminals B+ and D+ exceeds a
certain level. The output from the alternator G and available
between terminals B+ and B- is used to supply various loads (not
shown) and additionally is permanently connected to a battery 11
which supplies power to the loads when the alternator G is not
running, for example when its driving engine is stopped. Under
ordinary normal operating conditions, the voltage across terminals
B+ and B- so controls voltage regulator 6 that the battery 11 is
properly charged without, however, permitting the voltage to rise
to a level which may cause an overcharge of the battery. In
accordance with the present invention, a circuit interrupting
element 12, shown as a fuse in FIG. 1, is connected in series with
the circuit supplying current to the field 5, typically in series
between voltage regulator 6 and the B- or chassis connection of the
network system. The fuse 12 is controlled to burn out if the switch
7, as shown the transistor, should become continuously conductive
so that the terminal P1 of the voltage regulator is permanently
connected to ground or chassis, causing maximum excitation current
to flow continuously through the field winding 5. Such continuous
current flow would result in excessive charge voltage being
supplied to the battery 11 and damage thereto and its eventual
destruction.
The interrupting element 12 is normally conductive and introduces
practically no resistance in the supply circuit to the field 5.
Normal operation of the power system for the vehicle thus is not
impaired.
Continuity of conduction of current of the circuit element 12,
typically the fuse, is controlled by an over-voltage sensing
circuit 13. Circuit 13, functioning as a monitoring circuit, senses
the voltage at the terminal D+ which, essentially, is identical to
the voltage of the positive current supply bus at B+, and compares
this voltage with a reference value. The comparison is done by a
Zener diode 14 connected to the tap or junction point of a voltage
divider 17 formed of resistors 18, 19 and connected between the D+
bus and the junction between voltage regulator 6 and the fuse 12,
represented by a connecting line 16. The comparison voltage can
also be derived at other points in the network, for example
directly from between buses D+ or B+ and B-. The monitoring circuit
13 additionally includes a semiconductor switch, typically a
thyristor 15, connected in parallel to the circuit formed by the
field 5 and the voltage regulator 6. A capacitor 21 bridges at
least one of the resistors 18, 19 of voltage regulator 17.
Operation: If the voltage regulator 6 is functioning properly, the
system will operate as well known in connection with automotive
electrical supply systems. If the transistor 7 or another similar
switching element should alloy or otherwise short-circuit so that
it will become continuously conductive, the generator voltage at D+
will rise; when the level of the voltage reaches the breakdown
voltage of Zener diode 14, as divided and applied at the tap point
of the voltage divider 17, thyristor 15 will fire and become
conductive. This short-circuits the buses D+ and B- and causes
short circuit current to flow through fuse 12. The fuse 12 will
burn out and interrupt the circuit to the field. This causes the
alternator G to lose excitation, and the alternator voltage will
drop to approximately zero.
Although not necessary, it is preferred to connect a resistor 20
between the terminals D+ and B- in order to provide a closed
circuit path for the lamp 9 through switch 10 even after
interruption of the circuit through field 5 so that the charge
control lamp will light. The charge control lamp will remain lit
and indicate a defect in the charge system immediately upon
burn-out of fuse 12, that is, immediately upon clearing of the
defective voltage regulator 6 from the circuit.
The charge control lamp 9, remaining brightly lit, thus will
indicate to the operator not only failure of the alternator to
supply current to battery due to defects in the alternator or in
the voltage regulator based on under-voltage conditions, but also
defects of the voltage regulator which could become destructive to
the battery and to the electrical system and elements connected in
the network.
The capacitor 21, preferably connected across resistor 19, prevents
application of stray voltage peaks to the Zener diode 14 and hence
undesired random and erroneous response of the thyristor 15
although the regulator 6 is functioning properly and is in order.
Such stray voltage peaks may be caused due to switching transients,
and the like, occurring in the on-board network. The capacitor
provides for filtering of such peaks and prevents breakdown of
Zener diode 14 due to short-time transients.
Embodiment of FIG. 2: This embodiment is essentially identical to
that of FIG. 1 and identical elements have been given the same
reference numerals and will not be described again; similar
elements have been given reference numerals with prime
notation.
The circuit of FIG. 2 differs from that of FIG. 1 in that a
connecting line 22 from the voltage regulator 6 is provided,
connected not to a fuse 12 but, rather, to a normally closed (NC)
switch terminal 23 which is controlled by a relay coil 24. The
relay coil 24 is connected in series with the main current path of
thyristor 15'. Thyristor 15' is serially connected between the
terminals B+ and B-. The voltage divider 17' likewise is connected
between the terminals B+ and B-, and contains resistors 18', 19'
forming a junction which is connected to a Zener diode 14'. There
is no change in response of the monitoring circuit 13'. If voltage
regulator 6 becomes defective by being continuously conductive,
Zener diode 14' will respond and relay coil 24 will be energized,
breaking the NC connection through terminal 23 between the voltage
regulator 6 and the chassis or B- bus. Excitation of the alternator
thus is interrupted. Indication of malfunction can be through the
charge control lamp 9 if resistor 20 is provided, connected as
shown. An additional indication or an indication in lieu of that
provided by resistor 20 is possible, by connecting a lamp 25 in
series with the thyristor 15' and the relay coil 24. Thus, an
additional indicator lamp is provided which can indicate the nature
of the malfunction of the voltage regulator. This circuit has the
advantage that, if the malfunction of the voltage regulator 6 is
temporary, for example self-healing due to a sticking relay, the
circuit can be cleared by disconnecting one of the connecting
cables to the battery 11. It is also possible, and recommended, to
provide an additional control line 26 from terminal P2 of the
ignition switch 10 to the lamp 25. Line 26 then will be energized
only when the ignition switch 10 is closed. Upon opening of the
ignition switch 10, the monitoring circuit is then disabled and
will reset, for repeated operation and supervision of proper
operation of the voltage regulator upon reclosing of switch 10.
Capacitor 21' is used similarly to capacitor 21, FIG. 1.
Various charged and modifications may be made, and features
explained in connection with any one of the embodiments may be used
with any of the other, within the scope of the inventive
concept.
* * * * *